1) The French may be more likely to engage in Blue Zone activities (walking, social interaction, eating more slowly)

2) They may consume more mTOR inhibitors (coffee, cigarettes, alcohol, chocolate) that inhibit weight gain (and to some degree inflammation), even if some of those things also degrade health on other levels.

3) Apparently, the preservatives calcium propionate/proprionic acid (often used in American bread and cheese) are being reviewed for causing weight gain. In France and other parts of Europe, those preservatives are evidently not used (the bread and cheese have less shelf-life, but people are healthier).

4) There was never a confirmed medical follow-up to the colloquialism "red wine helps your digestion" (it just gives me heartburn & often sinus headaches). Maybe it works for the French since they acclimate at an early age.